Generally, an airbag is an apparatus for protecting a driver and passengers by providing a gas into the airbag by exploding gunpowder so as to inflate the airbag after detecting a crash impact with an impact detecting sensor, when a driving car collides head-on or side-on at a speed of about 40 km/h or more.
Recently, as interest in safety of passengers has risen along with functionality and convenience of a car, the current trend is an increase in the importance of safety devices which can protect the passengers from a car accident. Among the safety devices, particularly, the airbag system is used in company with a seat belt and functions to prevent the passenger from being injured when a car collides head-on or side-on. Furthermore, among the airbag systems, an airbag system particularly related to the side collision of a car is generally separately used as a curtain airbag for protecting a head part of the passenger and a side airbag for protecting a side part of the passenger. Here, the curtain airbag generally has a structure which is installed along the interior upper side of a car and is inflated like a curtain when a car collides, and the side airbag is installed in the door or the side of the seat and prevents the side part of the passenger from being injured due to direct bumping against the car body, including the door.
Particularly, a side-curtain-type airbag means an airbag installed at the side window or structure of a car for the purpose of preventing passengers from being wounded by the side window or structure when the car turns over. A common airbag installed at the front of a car can prevent passengers from receiving secondary shock by the airbag and can secure a driver's view only if it is quickly inflated by an explosive gas when the car crashes and the gas in the airbag is discharged in a short time. For this, most common airbags installed at the front of car have holes for discharging air. However, the side-curtain-type airbag is a means for protecting a passenger's head from the side window or structure of a car when the car turns over, and thus the side-curtain-type airbag must be inflated for supporting passenger's head safely for at least 6 seconds when the car turns over. For this, the gas should not leak more than needed from the seam part of the fabric of the airbag. Therefore, side-curtain-type airbags generally do not have holes for discharging air.
Therefore, a study for developing an airbag having excellent mechanical properties and inflating performance is needed, in order to achieve the internal pressure maintenance performance and the airbag inflating performance sufficiently to safely protect passengers from the accidents such as a car rollover, namely, in order to transfer the inflating gas to the airbag cushion effectively.